DETONATOR PACKAGING SYSTEM

Abstract: A packaging system for storing and transporting detonating devices includes a plurality of subpack containers (12) disposed in an overpack container (24), the subpack containers being dimensioned and configured to contain therein a plurality of unsegregated detonating devices, and an overpack pad (26a) disposed in the overpack container between adjacent cupback containers. Alternatively, the system comprises at least one subpack assembly (10) including a subpack container having disposed therein a divider (14, 16) defining a plurality of compartments in the subpack container, each compartment being sized to contain a plurality of unsegregated detonating devices. There is a subpack pad means (18) disposed between adjacent compartments in each subpack container to limit the propagation of the detonation of one or more detonating devices and an overpack container (24) within which is disposed at least one subpack container.

Description: DETONATOR PACKAGING SYSTEM BACKGROUND OF THE INVENTION Field of the Invention This invention relates to packaging systems and more particularly to systems for packaging and shipping detona¬ tors. The need to transport commercial quantities of deto- nating devices gives rise to concerns regarding the safety with which packages containing the detonating devices can be stored and moved, because the packages may be exposed to a wide range of temperatures and may be subjected to a variety of physical stresses, e.g., impacts that may occur should the package be dropped. In designing a packaging system for detonators, attention must be given not only to preventing unwanted detonation of the detonators in the package during shipment,and handling, but also to prevent the propagation of inadvertent detonation from one package to another. The prior art generally addresses these con¬ cerns through the use of dense packaging materials and by disposing detonators singly in isolated compartments. Related Art U.S. Patent 2,868,360 to Donkin dated January 13, 1959 discloses a storage container for detonators in which an outer box is divided by an interior partition into two main compartments, and wherein each compartment is divided into cells by a separator assembly. A single detonator is disposed within each cell. U.S. Patent 2,601,919 to Darbyshire dated July 1, 1952 discloses a container for packaging electrical deto¬ nators comprising an outer box that holds a plurality of compartmentalized inner boxes. Each compartment is dimen- sioned and configured to hold a single detonator and asso¬ ciated leg wires. U.S. Patent 2,352,998 to Alexander et al dated July 4, 1944 discloses a packaging system for electrical blast- ing caps and their associated leg wires in which each cap and its leg wire is disposed within a cardboard tube, and a plurality of the tubes are contained within a box. U.S. Patent 1,631,756 to Olin dated June 7, 1927 dis- closes a tube arrangement for packaging a single detona¬ tor. U.S. Patent 4,586,602 to Levey dated May 6, 1986 shows a transport system for transporting detonating cord in which the detonating cord is looped around cardboard support members and packed in a cardboard box surrounded by cardboard baffles. The Applicants have previously used a packaging sys¬ tem comprising an overpack container within which was dis¬ posed a plurality of subpack containers, each subpack con- tainer holding a plurality of unsegregated detonating de¬ vices. This package met 4G fiberboard container require¬ ments and was assigned a hazard classification of LIB for the shipment of detonating devices containing up to about 985 mg of explosive material per unit and a total of 100 grams of explosive material per subpack container. SUMMARY OF THE INVENTION In accordance with the present invention there is provided a packaging system for storing and transporting detonating devices comprising the following components. A plurality of subpack containers is disposed in an overpack container, the subpack containers being dimensioned and configured to contain therein a plurality of unsegregated detonating devices. An overpack pad means is disposed in the overpack container between adjacent subpack contain¬ ers. In accordance with another aspect of the invention, a packaging system for storing and transporting detonating devices comprises the following components. At least one subpack assembly comprising a subpack container has dis¬ posed therein divider means defining a plurality of com¬ partments in the subpack container. Each of these com¬ partments is dimensioned and configured to contain a plur- ality of unsegregated detonating devices. Subpack pad means are disposed between adjacent compartments in each subpack container for inhibiting the transfer of energy generated from detonation of one or more detonating de- vices contained within the subpack container from one compartment to the adjacent compartment. The subpack container or containers are contained within an overpack container. In another embodiment of the present invention, the subpack assembly and the overpack container may comprise corrugated board, e.g., 4G corrugated board containers. In certain embodiments, the subpack container comprises corrugated board having a bursting strength of at least about 200 lbs/in , and the overpack container comprises corrugated board having a bursting strength of at least about 275 lbs/in 2 . Another aspect of the invention provides for a plur¬ ality of detonating devices disposed in each compartment with each detonating device individually comprising not more than about 800 mg of explosive material. In a re¬ lated embodiment, each plurality of detonating devices comprises not more than about 25 grams of explosive mate¬ rial in each compartment. Yet another aspect of the present invention provides that adjacent detonating devices are disposed with their respective detonator caps at respective opposite sides of the compartment within which they are disposed. The present invention further comprises a packaging system for storing and transporting detonating devices, as follows: A plurality of subpack assemblies each compris¬ ing a subpack container comprising corrugated board having a bursting strength of at least 200 lbs/in 2 have disposed therein divider means comprising double-wall B- and C- flute or stronger corrugated board to define a plurality of compartments of the subpack assembly. Each compartment is dimensioned and configured to contain a plurality of unsegregated detonating devices, the subpack assembly fur¬ ther comprising subpack pad means comprising a double lay- er of double-wall B- and C-flute or stronger corrugated board and being disposed between adjacent compartments for inhibiting the transfer of energy generated by detonation of one or more detonators contained within the subpack as- sembly from one compartment to the adjacent compartment. The subpack assemblies are disposed within an overpack container comprising corrugated board having a bursting strength of at least 275 lbs/in 2 . A method aspect of the invention provides a method fo r packaging detonating devices comprising the following steps: (1) placing a plurality of unsegregated detonating devices in each of a plurality of subpack containers; (2) placing the subpack containers in an overpack container; (3) placing overpack pad means between adjacent subpack containers; and (4) sealing the overpack container. Yet another method in accordance with the present in¬ vention provides a method for packaging detonating devices comprising the following steps: (1) placing a plurality of unsegregated detonating devices in each of at least two compartments of each of at least one subpack assembly, each subpack assembly comprising (a) a subpack container, (b) divider means in the subpack container defining at least two compartments in the subpack container, and (c) subpack pad means disposed between adjacent compartments for inhibiting the energy generated by detonation of one or more detonators contained within the subpack assembly from one compartment to the adjacent compartment; (2) placing each subpack assembly in an overpack container; and (3) sealing the overpack container. Other aspects of the invention include carrying out the method aspects using the above-described packaging systems. Still other aspects of the invention are de¬ scribed below. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is an exploded perspective view of one embodiment of a subpack assembly suitable for use in a packaging system according to the present invention; Figure 2 is a perspective view of one embodiment of a packaging system according to the present invention com¬ prising two subpack assemblies in an overpack container; Figures 3A and 3B are perspective views of other embodiments of a packaging system according to the present invention, each comprising three subpack assemblies; Figure 4 is a schematic plan view of a shock tube, illustrating a figure of 80 coiling pattern; Figure 5 is a schematic plan view of a detonating device comprising a shock tube coiled in a figure of 80 pattern; and Figure 6 is a schematic plan view of a packaging assembly of a comparative example of a subpack container and subpack pads without divider means. DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a packaging system for storing and transporting detonating devices in a man¬ ner that is inexpensive, easy to use and which meets mod- ern safety standards prescribed by legal authorities. The level of safety provided by the present invention is re¬ flected in its qualification under the United States De¬ partment of Transportation Classification 1.4B set forth at 49 CFR when used to ship detonating devices as de- scribed below. Generally, this safety classification in¬ dicates that not only does the package meet the require¬ ments of packages designated LIB, indicating acceptable stability with respect to ambient temperature variations and physical impact, but the package further satisfies the requirements identified as a Series 6 Test promulgated by the United Nations and adopted by the United States De¬ partment of Transportation when used with a particular class of detonating devices as described below. As a result of the superior safety and packaging integrity exhibited by packaging systems according to the present invention, numerous national governments will allow non-electric detonating devices for blasting opera¬ tions to be shipped on the same vehicle with materials classified as 1.1 or 1.2 or 1.3, e.g., secondary blasting charges provided they are placed in an IME 22 container or other containers specified by applicable regulations. This means that when quantities allow, detonating devices and the secondary charges with which they are to be used can be transported together in a single vehicle when they otherwise may not: prior art packages rated as LIB could not be shipped in this way. In addition, packages classi¬ fied as 1.4B can be shipped by means not available to those classified as 1.1B, e.g., by cargo air. These ad¬ vantages can lead to significant savings in shipping costs. Although a variety of packaging container materials may be employed to produce a packaging system that quali- fies as classification 1.4B, the range of materials that are generally commercially acceptable for packaging sys¬ tems is somewhat limited. Suitable packaging materials must pass the specified safety tests, yet must not contri¬ bute unduly to the overall weight of the package and must be easy to assemble, load and dispose of. Thus, although it may be possible to produce a packaging system for deto¬ nators that is classifiable as 1.4B using, e.g., metal or plywood, such a packaging system may be unacceptable due to its excessive weight and difficulty in manufacture, storage prior to use and disposal thereafter. The detonating devices contemplated for such use with the present invention generally comprise non-electric detonator caps for blasting such as those commonly used to detonate borehole explosives in blasting or mining opera- tions. A typical detonating cap assembly is disclosed in U.S. Patent 3,981,240 to Gladden, dated September 21, 1976, the disclosure of which is hereby incorporated here¬ in by reference. Typically, detonator caps comprise a metallic shell within which is disposed a charge of explo- sive material such as PETN. The detonator caps are con¬ ventionally attached to an ignition signal transmission line which typically comprises shock tube such as that disclosed in U.S. Patent 3,590,739 to Persson dated July 6, 1971, the disclosure of which is hereby incorporated by reference. Shock tube, as is known in the art, is an ex¬ truded tube of polymer material having a hollow core and a relatively small quantity of explosive material, e.g., HMX, disposed on the inner wall. When the explosive mate¬ rial at one end of the tube is ignited, an ignition pulse travels quickly along the length of the tube and can be used to initiate a detonation reaction at the other end. Due to the great speed with which the detonation signal travels, the signal is conventionally described as travel¬ ing instantaneously along the tube. However, as used herein and in the claims, "shock tube" is meant to include any suitable detonation signal transmission tube, includ¬ ing low velocity signal transmission tube, or the like. Often, a delay element is disposed in the cap, to cause a delay between the arrival of a signal from the shock tube and the detonation of the explosive,material in the cap. A delay element typically comprises a relatively slow burning material that causes a delay of between a few milliseconds to several seconds in the transmission of the initiation signal to the explosive charge. A package of non-electric detonators for blasting can only be accorded classification 1.4B if, among other cri¬ teria, the explosion of any one detonator in the package will not cause the other detonators to "mass detonate", and will cause only limited propagation of the detonation. Mass detonation means that more than 90 percent of the devices in the package explode practically simultaneously, and limited propagation means that the maximum amount of explosive material that explodes upon inadvertent or spon¬ taneous detonation does not exceed 25 grams. (See 49 CFR Section 172.101 Hazardous Materials Table for detonator assemblies, non-electric, for blasting, Identification Number UN 0361, indicating the applicability of Special Provision 103, which is set forth in Section 172.102.) To limit the propagation of inadvertent detonation, the prior art teaches that it is necessary to individually isolate each detonator from the others by disposing the detonator in an individual compartment. However, the Applicants have found that propagation of the detonation reaction in a package can be acceptably curtailed even if a plurality of " detonators are disposed together in a compartment in the package. It is preferred in the practice of the pres¬ ent invention that the quantity of explosive material for each detonating device be not more than about 800 mg. A packaging system according to one embodiment of the present invention comprises a subpack assembly comprising a subpack container and divider means for defining at least two compartments in the subpack container. Each compartment is dimensioned and configured to receive a plurality of unsegregated detonating devices typically comprising detonator caps and associated lengths of shock tube. The divider means may comprise corrugated board com¬ partment baffles or enclosures that may be folded to de¬ fine a compartment. Typically, each compartment has a substantially rectangular configuration, and the enclo- sures establish at least five walls of their respective compartments. Optionally, the divider means may comprise compartment boxes dimensioned and configured to be dis¬ posed within the subpack container and to completely en¬ close the compartment on six sides. As used herein and in the claims, the term "box", when used in reference to di¬ vider means, is intended to include not only assembled and self-supporting containers but also enclosure baffles or templates which are folded into box-like configurations but which are not self-supporting. Subpack pad means are disposed between compartments in the subpack container to provide insulation which in¬ hibits the travel of the brisance or energy of the detona¬ tion between compartments, so that in the event of inad¬ vertent detonation of a detonator cap in one compartment, the energy is inhibited from traveling through the divider means into the neighboring compartment in the subpack con¬ tainer. Thus, the subpack pad means inhibits propagation of the detonation reaction between compartments. -9- Since the compartment enclosures within the subpack container define at least five walls of their respective compartments, and since compartment boxes completely enclose their compartments, the subpack container and the divider means therein generally provide a double layer of corrugated board about the compartments for containing energy that may be released upon inadvertent detonation of a detonator cap therein. The packaging system of the present invention further comprises an overpack container within which at least one, but generally a plurality, e.g., two or three, of the sub- pack assemblies are disposed. The overpack container pro¬ vides at least an additional single layer of corrugated board to inhibit the energy released by inadvertent deto- nation from any subpack assembly therein to other pack¬ ages. In addition, the overpack container provides an added degree of thermal insulation and physical integrity to the package. Overpack pad means disposed in the over- pack container between the subpack containers to assure a tight fit of the subpack containers within the overpack container, i.e., to prevent jostling of the subpack assem¬ blies and to provide further physical insulation against the propagation of a detonation reaction between the sub- pack containers by inhibiting the energy released upon detonation of a cap in the package between adjacent sub- pack assemblies. Advantageously, the subpack container and overpack container of the present invention qualify as 4G contain¬ ers as described in Title 49 of the Code of Federal Regu- lations. Chapter 1, Section 178.516. Generally, such ma¬ terial must resist water at the outer surface such that an increase in mass, as determined in a test carried out over 30 minutes by the Cobb method of determining water absorp¬ tion, is not greater than 155 grams per square meter. The fiberboard must be capable of creasing without cutting through the facings, and the facings must be firmly glued to the fluting. According to the present invention, a packaging system is constructed using such corrugated board material to create compartments within which plural¬ ities of unsegregated detonating devices are disposed. A typical subpack assembly for use in the present invention is shown in Figure 1. Subpack assembly 10 cora- prises a subpack container 12, divider means provided by boxes as defined above, e.g., compartment enclosures 14 and 16 and a subpack pad means provided by subpack pad 18. Enclosures 14 and 16 which are similarly configured, are dimensioned and configured so that they can be folded from an initial flat configuration to provide panels which de¬ fine compartments where detonating devices may be dis¬ posed, and are further dimensioned and configured to be simultaneously contained in the folded configuration with¬ in subpack container 12. Thus, subpack container 12 is divided into two compartments for holding detonating de¬ vices. Subpack pad 18 may be made from any suitable mate¬ rial such as one or more layers of corrugated board, and is preferably dimensioned and configured to engage the en¬ tire faces of the compartments between which it is dis- posed. Subpack pad 18 serves to inhibit the energy that may escape enclosures 14 or 16 or any alternate divider means upon detonation of a detonating device in either one of the compartments into the other compartment. Enclo¬ sures 14 and 16 are further dimensioned and configured so that respective top panels 14a and 16a can be raised while enclosures 14 and 16 are disposed within subpack container 12, to allow the user to assemble the subpack assembly and then dispose detonating devices in the compartments. When the desired quantity of detonating devices has been packed into the respective compartments, panels 14a and 16a are folded down so that subpack lid 20 can be folded over to close subpack container 12. Preferably, as shown in Fig¬ ure 1, each compartment enclosure 14 and 16 provides pan¬ els that define at least five walls of a rectangular com- partment. A sixth wall may also be defined by enclosures 14 and 16, or at least partially defined, as by partial panels.16b, which at least partially define a sixth wall of the rectangular compartment 16c. As discussed below, -li¬ the open, or partially open, sixth wall should be disposed at an end of the subpack container. In accordance with the present invention, one or more subpack assemblies is disposed within an overpack contain- er. Thus, Figure 2 illustrates a packaging system accord¬ ing to the present invention in which two substantially identical subpack assemblies 10 and 10' each having there¬ in two compartments, are disposed within an overpack con¬ tainer 24a. Like subpack assemblies 10 and 10', overpack container 24a may be made from a suitable corrugated board material. In other embodiments, such as shown in Figures 3A and 3B, the overpack container may be dimensioned and config¬ ured to hold three subpack assemblies. Thus, an overpack container such as 24b may be dimensioned and configured to hold three subpack assemblies 10, 10' and 10'' in a "π" configuration, i.e., with two subpack assemblies 10' and 10'' side by side and the third subpack container 10 dis¬ posed crosswise at the ends of the side by side containers as shown in Figure 3A, or to hold all three subpack assem¬ blies in parallel, side by side relation as overpack con¬ tainer 24c shown in Figure 3B. With the subpack assembly disposed within the overpack container, the overpack con¬ tainer provides at least one additional layer of corru- gated board about the compartments where the detonating devices are stored, resulting in a degree of insulation that is adequate, given the restrictions on the quantity and concentration of explosive material in the compart¬ ments and the proper choice of corrugated board material as taught herein, to prevent propagation of detonation reactions from one package to another even if the entire contents of any one compartment explode simultaneously. The packaging system of the present invention further includes overpack pad means such as overpack pad 26a of Figure 2 and pads 26a and 26b of Figure 3A. These over- pack pads are similar in construction to the subpack pads described above and serve both to prevent the subpack as¬ semblies from jostling within the overpack container and the subpack assemblies from jostling within the overpack container and to inhibit the energy released from any in¬ advertently detonated device from traveling from one sub- pack assembly to an adjacent subpack assembly. Without wishing to be bound by any particular theory, it is believed that leaving the ' sixth wall of the compart¬ ment partially open and directed toward the side of the subpack container is a preferred embodiment of the present invention because the surrounding enclosure panels and the subpack pad serve to direct the energy of detonation of a detonator therein away from the adjacent compartment. The wall of the subpack container, exposed via the partially open sixth side of the compartment, inhibits the passage of energy therethrough. Should detonation energy pass through the wall, it is further inhibited by one of (i) the wall of an adjacent subpack container (see Figure 3A) , (ii) an overpack pad, or (iii) the wall of the overpack container. For example, in the embodiment of Figure 3A, detonation energy penetrating, e.g., subpack assembly 10' toward subpack assembly 10, would be inhibited from enter¬ ing the adjacent compartment in subpack assembly 10 by (i) the wall of the subpack container of assembly 10, (ii) a side panel of the enclosure defining the compartment in assembly 10' and (iii) the overpack pad 26a. On the other hand, energy directed toward another package, e.g., from assembly 10, would be inhibited by (i) the wall of over- pack container 24b, (ii) the wall of the adjacent overpack container, (iii) the wall of the subpack assembly in the adjacent overpack container and, probably, (iv) a side panel of the enclosure baffle in the adjacent subpack as¬ sembly. Tests have shown that these impediments are ef¬ fective to prevent propagation of detonation reactions from one package to another, even when the contents of a compartment detonate substantially simultaneously. How- ever, the use of an enclosure baffle to provide an open- sided compartment should not be construed to be a neces¬ sary limitation on the invention. As stated above, the materials used to produce the subpack containers, enclosures or other divider means, subpack pads, overpack containers and optional overpack pads may be made from any suitable corrugated board. The subpack container and the overpack container meet the per- formance criteria of specification 4G for corrugated con¬ tainers. Suitable fiberboard products meeting these cri¬ teria are available from the Longview Fibre Company of Springfield, Massachusetts. In a particular embodiment of the present invention, the subpack container was dimen- sioned and configured to define a rectangular box having a length of about 16.6 inches (42.16 cm), a width of about 8.35 inches (21.21 cm) and a height of about 8.25 inches (20.95 cm) and was made from a B-flute fiberboard having a bursting strength of 200 lbs/in 2 and a combined minimum facings weight of 84 lbs/m.sq.ft. Enclosures 14 and 16 were made from double-wall (B-flute and C-flute) corru¬ gated board. The subpack pad 18 was made from the same corrugated board as the enclosures, but was folded over to double its thickness. Alternatively, the subpack pad may be made from a triple-wall C-flute corrugated board. The overpack container was made from a C-flute corrugated board reported to have a bursting test strength of 275 lbs/in 2 and a minimum combined facings weight of 138 lbs/m.sq.ft. A suitable overpack pad was formed from the same material as the subpack pad, and was similarly folded over to double its thickness. Those skilled in the art will recognize that some variations in the materials selected for the subpack container, enclosure baffles and pads and overpack container may be made without departing from the invention, and that the limits of such varia¬ tions, given the disclosure herein, can be ascertained without undue experimentation. In choosing the dimension of the subpack container, certain presumptions must be made with respect to the quantity of explosive in each detonating device to be packaged and the length of shock tube attached thereto, because both factors determine the maximum number of units that can be disposed in the compartment. The quantity of - 14 - explosive in each unit is important because the subpack container may be inadequate to contain the detonation of even a single device if the quantity of explosive material therein is excessive, and because larger charges are ex- pected to cause other devices in the compartment to deto¬ nate, presenting a propagation problem. The length of shock tube also affects the number of units that can be disposed in the compartment, because of its bulk and the great variations in length that can accompany detonator caps, e.g., from 8 to 60 feet. For example, a subpack container dimensioned and configured to have compartments capable of holding up to thirty-five detonating devices each having twenty feet of associated shock tube may be considered to be oversized with respect to detonator caps comprising 800 mg of explosive material per device; a fewer number of such devices would be packed together to assure limited propagation under Special Provision 103, so a smaller sized compartment would be used. Yet, the same compartment may be considered to be undersized with re- spect to similar devices having 60 feet of shock tube per unit, the bulk of the longer shock tube requiring more space in the container and therefore filling the container before the permitted number of detonator caps is disposed therein. Similarly, the container would be undersized with respect to devices comprising thirty feet of shock tube and a detonator cap comprising only 300 mg of explo¬ sive material each; a greater number of unsegregated units could be disposed together than the compartment could ac¬ commodate, due to the lesser quantity of explosive materi- al in each unit. The dimensions for the subpack container given above are considered to be adequate to produce a 1.4B package for commercially useful quantities of deto¬ nating devices that may comprise from 8 to 60 feet of shock tube and from about 190 mg +/- 20 mg to about 745 mg +/- 50 mg of explosive material per unit (not counting the shock tube core material for reasons discussed below) . When the length of shock tube or the relatively low quan¬ tities of explosive material per detonating device allow, the subpack pad and divider means may be omitted from the subpack assembly; the detonating devices may be placed directly in the undivided subpack container, provided that the overpack pads are placed between adjacent subpack con- tainers in the overpack container. While the compartment may be viewed as undersized with respect to the smaller of these detonators (190 mg), it performs adequately for the more powerful of them (745 mg) and therefore can be used with confidence for a wide range of products of smaller detonator charges. Should the more powerful detonator units (745 mg +/- 50 mg each) have shorter associated shock tubes, there may be empty space in the compartment once the maximum number of units is placed therein. Rath¬ er than placing additional units in the compartment and risking a violation of 1.4B restrictions, the remaining volume should be filled with inert dunnage. Thus, it is seen that the dimensions for the subpack container given above allow for the creation of compartments that contain the greatest number of the most powerful allowed detonator caps having the longest commercially desirable length of shock tube. To illustrate how the maximum allowable number of units of detonating devices may be disposed in a compart¬ ment, consider a device produced by The Ensign-Bickford Company under the trade designation EZ Det*, which com¬ prises a length of shock tube having a so-called microcap at one end comprising about 190 mg +/- 20 mg of dextri- nated lead azide and a detonating cap at the other end comprising 95 mg +/- 10 mg of dextrinated lead azide for initiating a detonating charge of 460 mg +/- 20 mg PETN. Assuming that the microcap and the detonator cap each have their maximum quantities of explosive materials, the maxi¬ mum total explosive material in an EZ Det β device is about 795 mg, i.e., about 800 mg. The term "explosive material" as used herein and in the claims is intended to include any material suitable for use in detonator caps for blast¬ ing purposes, including PETN, dextrinated lead azide and the like. The shock tube may vary in length, e.g., from 8 to 60 feet (i.e., between about 2.4 and 18.4 meters) and may contain a mixture of HMX and aluminum in an amount of only about 0.016 grams per meter, for a total maximum con¬ tribution of less than 1 gram of explosive material. Shock tube is known to survive the detonation of the ex¬ plosive material it contains because the linear density of the explosive material is so low, so the explosive materi¬ al in shock tube is not included in the limitations re¬ garding explosive material per detonating device or the total per container for purposes of the present invention. Due to the strength, i.e., the relatively large quan¬ tity of explosive material in the detonator cap of an EZ Det* device, the detonation of any one device sets off other devices in the same compartment. Therefore, to sat- isfy the limited propagation requirement of Special Provi¬ sion 103 the maximum number of EZ Det* units that can be disposed in the same compartment under a 1.4B classifica¬ tion is about 25 g / 0.800 = about 31 units. In practice, each compartment is limited to 30 units, because the then fully packaged container will hold a commercially conve¬ nient quantity of units. When shipping detonating devices comprising detonator caps and associated lengths of shock tube in a packaging system according to the present invention, it is preferred to wind the shock tube in a "figure of 80" pattern as de¬ scribed in U.S. Patent 5,129,514 to Lilley, Jr. dated July 14, 1992, the disclosure of which is hereby incorporated by reference. To briefly summarize the teaching of the Lilley, Jr. Patent, a figure of 80 configuration may be achieved by choosing one end of a shock tube 28, Figure 4, as the starting end 30 and establishing an S-shape by dis¬ posing shock tube 28 in the directions indicated by arrows 32 and 34. A length of the tube may continue straight up (as sensed in Figure 4) as shown by arrow 36 and may then wind around the top of the S and straight down as indi¬ cated by arrow 38, completing the "0" of the "80". The shock tube 28 is then disposed along the bottom of the S, and then traverses the S as indicated by arrow 40 to es- tablish a figure 8 within the encircling figure 0, thus creating the figure of 80 pattern. For ease of illustra¬ tion, the detonator cap associated with shock tube 28 is not shown in Figure 4. When the winding is complete, a single frangible band, e.g., paper packaging tape 42, Fig¬ ure 5, may be used to secure the figure of 80 pattern in place. Alternatively, the frangible band may be used to secure together a plurality of detonating devices each comprising a length of shock tube coiled in a figure of 80 pattern. In the embodiment of Figure 5, the detonating device comprises a detonator cap 44 at one end and a so- called microcap 46 at the other end. As can be seen in Figure 5, the detonator cap 44, which comprises the largest proportion of explosive material in the device, is disposed at the lower end of the figure of 80 pattern, while the microcap is disposed near the middle of the coil. When the figure of 80 winding is used in such prod¬ ucts, it is preferred to alternate the position of the detonator caps between adjacent detonating devices so that they are not in close proximity and so that the shock tube windings of one device are disposed next to the detonator cap of the other device to act as dunnage for its adjacent detonator cap to inhibit the energy that may be released from that cap upon accidental detonation. In addition to the foregoing, it is optional but pre¬ ferred to place the subpack assemblies in a sealed mois¬ ture barrier bag in the overpack container. The barrier bag may be made from polymer-metal foil laminate material, with a dessicant, to absorb moisture that may enter the packaging system over long-term storage and affect the performance of the detonating devices therein. Example 1 A detonator package according to the present inven- tion was prepared using an EZ Det* device as described above. Thirty EZ Det* devices were disposed in each of two compartments in a subpack assembly, and three such subpack assemblies were disposed in an overpack container measuring 27 inches X 17.5 inches X 9.5 inches. The subpack container material comprised a B-flute board having a bursting strength of 200 lbs/in as described above; the overpack container material comprised a C-flute board having a bursting strength of 275 lbs/in 2 . Three such packages were prepared so that the test could be repeated in three trials. In each trial, a complete package of detonators was placed on a steel witness plate and a detonator near the center of the package was primed. The package was sur¬ rounded with corrugated board containers of loose sand to provide 0.5 meters of confining material in all directions in compliance with the 6(a) test set forth in the Explo¬ sive Test Manual. The primed detonator was set off and the degree of propagation in the package and extensive damage to the confining material and to the witness plate were observed. In each trial, there was no damage to the witness plate beneath the package, no crater at the test site, no explosion of the package, and no disruption or scattering of the confining material. Further, propaga¬ tion of the detonation was limited to the compartment in which the primed detonator was located. Example 2 The tests described in Example 1 were repeated, ex- cept that the detonating devices were the EZTL products described above. The results were the same as in Example 1, except that only the primed detonator fired; there was no propagation within the package. Example 3 Packages prepared in accordance with Examples 1 and 2 were subjected to a 12 meter drop test in which three packages of each were dropped from a height of 12 meters onto their end, side and bottom, respectively. The pack¬ ages were observed for damage to the package and resulting reaction by the detonating devices. No damage was ob¬ served when the packages were dropped on their side or bottom; minimal damage occurred to packages of both prod¬ ucts when dropped on end. There was no fire or explosion resulting in any of the trials. 5 Example 4 Three complete packages containing 180 units each of the EZ Det* product were prepared as described in Example 1 and were subjected to an external fire test pursuant to test 6(c) of the Explosive Test Manual. The packages were 10. arranged in a steel stand and encircled with steel banding for support. Sufficient diesel fuel was poured into a re¬ ceptacle beneath the stand. The fuel was ignited using black powder and electric matches. No explosion, no haz¬ ardous projections (i.e., escaping energy) and no signifi- 15 cant thermal effects were observed in any of the three packages. Comparative Example 1 A subpack container 12' as described above was di- 0 vided into three sections A, B and C using two pads 18', 18'' but without using divider means such as compartment boxes or enclosures, as illustrated in Figure 6. Thirty units of the MS product each comprising a length of shock tube and a detonator cap having a maximum explosive weight 5 of 585 mg were disposed in each section, with all the caps in each section disposed at the same side of the contain¬ er; the caps in the middle section were disposed on a side opposite to the caps on the end sections, as illustrated in Figure 6. The subpack container was disposed on a wit- 0 ness plate and surrounded with confinement materials (con¬ tainers of sand) . A detonator cap in the middle section was primed and fired. After firing, it was found that the detonation propagated entirely within the central section and through the pads to the adjacent sections, so that all 5 the units in the subpack container fired. The witness plate showed 3 or 4 dents each about 1 inch in diameter. Since the total amount of explosive material that deto¬ nated was greater than 25 g and because damage was ob- served on the witness plate, this configuration was deemed not to be acceptable. Comparative Example 2 A package was prepared as described in Comparative Example 1, except that four sections in the box were de¬ fined by the use of three pads, without the use of com¬ partment boxes or enclosures and a total of 100 units were disposed in the subpack container, with 25 units in each section. The package was tested in the same manner as in Comparative Example 1. Upon detonation of a single, primed unit, the detonation propagated to all 100 units in the subpack container, and damage was caused to the witness plate. Comparative Example 3 Three subpack containers were prepared and packaged as described in Comparative Example 1 and were disposed in an overpack container. Overpack pads were disposed be- tween the subpack containers. In this comparative exam¬ ple, all the caps in each subpack container were disposed on the same side of the subpack container, and the subpack containers were disposed in the overpack container so that the detonator caps were proximate to the outer wall of the overpack container. A unit near the center of one subpack container was primed and fired. Eighty-eight of the 90 units in the test subpack container fired as well, showing that the detonation propagated through the pads within the subpack container. However, there was no propagation of the detonation from one subpack container to another through the overpack pads. Comparative Example 4 Three subpack containers were packaged as described above in Comparative Example 1, and the three subpack con¬ tainers were disposed in an overpack container. No sub- pack divider means, i.e., no enclosure boxes or baffles, and no overpack pads were used. Upon firing of a single test unit, no damage was caused to the witness plate, al¬ though the detonation propagated through the subpack pads to all 90 units in the subpack container causing a detona¬ tion of more than 25 g of explosive material. While the invention has been described in detail with reference to particular embodiments thereof, and while certain features of the invention may have been illu¬ strated in some embodiments of the invention and not in others, this is not intended as a limitation of the inven¬ tion, and it will be apparent that upon a reading and un¬ derstanding of the foregoing, numerous alterations to the described embodiments will occur to those skilled in the art and it is intended to include such alterations within the scope of the appended claims.

Claims: -28- A ENDED CLAIMS [received by the International Bureau on 16 September 1994 (16.09.94); original claims 1-5,8,12,13,18,19 20,24 and 25 amended; other claims unchanged (6 pages)] 1. A packaging system for storing and transporting detonating devices comprising: a plurality of subpack containers disposed in an overpack container, the subpack containers being dimen¬ sioned and configured to enclose therein a plurality of unsegregated detonating devices, and overpack pad means disposed in the overpack container between adjacent sub- pack containers for inhibiting the transfer of energy gen¬ erated by detonation of one or more detonators in one sub- pack container to the adjacent subpack container. 2. A packaging system for storing and transporting detonating devices comprising: at least one subpack assembly comprising a sub- pack container having enclosed therein a plurality of di¬ vider means each defining a compartment, to provide a plu¬ rality of adjacent compartments in the subpack container, each compartment being dimensioned and configured to con¬ tain a plurality of unsegregated detonating devices, and further comprising subpack pad means disposed between ad¬ jacent compartments in each subpack container for inhibit¬ ing the transfer of energy generated by detonation of one or more detonating devices in one compartment to the adja¬ cent compartment; and an overpack container within which is disposed the at least one subpack container, 3. The packaging system of claim 2 comprising a plu¬ rality of subpack assemblies, disposed within the overpack container, and further comprising overpack pad means dis¬ posed in the overpack container between adjacent subpack assemblies for inhibiting the transfer of energy generated by detonation of one or more detonators in one subpack as¬ sembly to the adjacent subpack assembly. 4. The packaging system of claim 2 or claim 3 com¬ prising two divider means in the subpack container * 5. The packaging system of claim 2 wherein the sub- pack assembly and the overpack container comprise corru¬ gated board. 6. The packaging system of claim 5 wherein each sub- pack container and the overpack container comprises 4G corrugated board containers. 7. The packaging system of claim 6 wherein the sub- pack container comprises corrugated board having a burst¬ ing strength of at least about 200 lbs/in 2 , and the over- pack container comprises corrugated board having a burst¬ ing strength of at least about 275 lbs/in 2 . 8. The packaging system of claim 7 wherein each di¬ vider means comprises a closed box defining one of said compartments. 9. The packaging system of claim 7 further compris¬ ing a plurality of detonating devices in each compartment and wherein each detonating device individually comprises not more than about 800 mg of explosive material. 10. The packaging system of claim 9 wherein each plu¬ rality of detonating devices comprises not more than about 25 grams of explosive material in each compartment. 11. The packaging system of claim 10 wherein adjacent detonating devices are disposed with their respective det¬ onator caps at respective opposite sides of the compart¬ ment within which they are disposed. 12. A packaging system for storing and transporting detonating devices, comprising: a plurality of subpack assemblies each comprising a subpack container comprising corrugated board having a bursting strength of at least 200 lbs/in 2 and having dis- posed therein divider means comprising double-wall B- and C-flute or stronger corrugated board and defining a plu¬ rality of adjacent compartments of the subpack assembly, each compartment being dimensioned and configured to con¬ tain a plurality of unsegregated detonating devices, the subpack assembly further comprising subpack pad means com¬ prising a double layer of double-wall B- and C-flute or stronger corrugated board and being disposed between adja¬ cent compartments for inhibiting the transfer of energy generated by detonation of one or more detonators in one compartment to the adjacent compartment? and an overpack container comprising corrugated board having a bursting strength of at least 275 lbs/in 2 and within which the subpack assemblies are disposed. 13. The packaging system of claim 12 further compris¬ ing overpack pad means comprising double-wall B- and C- flute or stronger corrugated board disposed in the over- pack container between adjacent subpack assemblies for in¬ hibiting the energy generated by detonation of one or more detonators in one subpack assembly to the adjacent subpack assembly. 14. The packaging system of claim 12 or claim 13 wherein the divider means comprises a plurality of com¬ partment boxes, each compartment box being dimensioned and- configured to define one of said compartments. 15. The packaging system of claim 14 further compris¬ ing a plurality of detonating devices in each compartment and wherein each detonating device individually comprises a length of shock tube and one or two detonating caps at¬ tached to the shock tube, the detonator caps containing not more than about 800 mg of explosive material per de¬ vice, exclusive of the material in the core of the shock tube. 16. The packaging system of claim 15 wherein each plu¬ rality of detonating devices comprises not more than about 25 grams of explosive material in each compartment, exclu¬ sive of any explosive material in the shock tube. 17. The packaging system of claim 16 wherein adjacent detonating devices are disposed with their respective det¬ onator caps at respective opposite sides of the compart¬ ment within which they are disposed, 18. A method for packaging detonating devices com¬ prising: enclosing a plurality of unsegregated detonating devices in each of a plurality of subpack containers; placing the subpack containers in an overpack container; placing overpack pad means between adjacent sub- pack containers for inhibiting the transfer of energy gen¬ erated by detonation of one or more detonators in one sub- pack container to the adjacent subpack container; and sealing the overpack container. 19. A method for packaging detonating devices com¬ prising- placing a plurality of unsegregated detonating devices in each of at least two adjacent compartments of at least one subpack assembly comprising (a) a subpack container, (b) a plurality of divider means in the subpack container, each defining a compartment in the subpack con¬ tainer, and (c) subpack pad means disposed between adja¬ cent compartments for inhibiting the transfer of energy generated by detonation of one or more detonators in one compartment to the adjacent compartment; placing each subpack assembly in an overpack con¬ tainer; and sealing the overpack container. 20. The method of claim 19 comprising placing a plu¬ rality of subpack assemblies in the overpack container and placing between adjacent subpack assemblies overpack pad means for inhibiting the transfer of energy generated by detonation of one or more detonators in one subpack as¬ sembly to the adjacent subpack assembly. 21. The method of claim 20 wherein each detonating device comprises not more than about 800 mg of explosive material. 22. The method of claim 21 wherein each plurality of detonating devices comprises a total not more than about 25 grams of explosive material in its respective compart¬ ment. 23. The method of claim 18 or claim 19 wherein each detonating device comprises at least one detonator cap and a length of a shock tube and wherein the method further comprises disposing adjacent detonating devices with their respective detonator caps at opposite sides of the com¬ partment within which they are disposed. 24. A method for packaging detonating devices com¬ prising: placing a plurality of unsegregated detonating devices each comprising a length of shock tube and one or two detonator caps attached to the shock tube, the detona¬ tor caps containing a total of not more than about 800 mg of explosive material exclusive of the material in the core of the shock tube in each of at least two adjacent compartments, each compartment being disposed in a subpack assembly comprising (a) a subpack container comprising corrugated board having a bursting strength of at least 200 lbs/in 2 , (b) a plurality of divider means comprising double-wall B- and C-flute or stronger corrugated board in the subpack container, each defining a compartment in the subpack container, and (c) subpack pad means comprising double-wall B- and C-flute or stronger corrugated board disposed between adjacent compartments for inhibiting the transfer of energy generated by detonation of one or more detonators in one compartment to the adjacent compartment; placing the subpack assemblies containing the detonating devices in an overpack container comprising corrugated board having a bursting strength of at least 275 lbs/in 2 ; and sealing the overpack container. 25. The method of claim 24 further comprising dispos¬ ing overpack pad means in the overpack container between adjacent subpack assemblies for inhibiting the transfer of energy generated by detonation of one or more detonators in one subpack assembly to the adjacent subpack assembly.

Inventors: SOBCZAK BRIAN R, THOMAS J DONALDSON, SOBCZAK, BRIAN, R., THOMAS, J., DONALDSON
Applicants: ENSIGN BICKFORD CO, THE ENSIGN-BICKFORD COMPANY
Application year: 1994
Main classification: F42B39
IPC codes: B65B5, B65B23, B65D5, B65D77, B65D81, B65D85, F42B39